text: ;For aluminium
  * sodium hydroxide
  * Keller's reagent
  ;For steels
  * hydrochloric and nitric acids
  * ferric chloride for stainless steels
  * Nital (a mixture of nitric acid and ethanol, methanol, or methylated spirits for mild steels.
  2% Nital is common etchant for plain carbon steels.
  ;For copper
  * cupric chloride
  * ferric chloride
  * ammonium persulfate
  * ammonia
  * 25-50% nitric acid.
  * hydrochloric acid and hydrogen peroxide
  ;For silica
  * hydrofluoric acid